In such a mold it is convenient to use a generally toroidal core peripherally divided into a number of ring segments to facilitate its extraction from the molded tire body after the same has been removed from the mold cavity. For this purpose it is necessary to have at least one segment whose sides are parallel to each other or diverge in a radially inward direction as seen from the shell axis. After this segment or segments have been extracted from the tire, the other segments can also be removed even if their sides converge in the direction of the axis.
Such a construction requires the several core segments to be precisely aligned in their working position and to be capable of resisting severe pressure differences. The maintenance of alignment can be accomplished, for example, with the aid of hook-shaped fittings overlappingly interlinking the segments in that position. In practice, however, the installation of such fittings requires a special machining of the contact surfaces of the ring segments, in order to preserve the necessary fluidtightness; the fittings, moreover, tend to interfere with the extraction of the segments from the molded tire body.